Which protocol is used to find the MAC address of one node whose IP address is known?a.IPb.TCPc.ARPd.DNS

The protocol used to find the MAC address of a node when the IP address is known is ARP (Address Resolution Protocol).

Here's a step-by-step explanation:

1. When a node needs to send a packet to another node on the same network, it first needs to know the recipient's MAC address.

2. The sender node knows the IP address of the recipient but not its MAC address. So, it uses the ARP protocol to find out the MAC address.

3. The sender node broadcasts an ARP request packet across the network, which contains the IP address of the recipient node.

4. Every node on the network receives this ARP request and checks the IP address in the packet.

5. The node with the matching IP address sends an ARP reply, which contains its MAC address, back to the sender.

6. The sender node receives the ARP reply and can now send the packet to the recipient using its MAC address.

So, the correct answer is c. ARP.